Remove Munro

I temporarily changed the colors, but the label will need more work. Maybe a bitmap font instead of actual text: there are some artifacts with scale animation

Make default.theme's panel background transparent
The panel now takes the width of the screen and anchors to the top of the window
closes #78

Refactor CircularButton to extend Button
Disable if Battler.can_use_skill is false
Closes #77

remove skill_to_use from base CombatAction class, move down to specialized SkillAction
rename skill_to_use -> skill

Also place them on the character's pawn at the start. They're not registered in the grid anymore so we can place them wherever we want
fix #72

closes #79

Added fixes based on Nathan's suggestions

Back on Par with Master

Slash still seems broken

Removed Print statements

Added Popup information with font #70 part 2

This replays the turn with the same battler, reopening the actions
select menu

Main changes:

- Simplified combat actions. Action handle the logic that relates to
their name. E.g. the attack-specific code is now in Attack.gd and not in
its parent class. Removed unused parameters. Removed actions selecting
their own target: this breaks the single responsibility principle (and
made the action code break when I changed stuff in the interface)
- Removed the old school UI and action_list code in favor of the
circular menu
- Almost all functions that dealed with one target now work with an
array of targets instead, even if the player only selects one target
- All commands should support working with multiple targets as a result

A lot of the changes I needed to make to accomodate for either feature
broke the game, so that's why I'm packing all the changes in a single
commit.

The button and tooltip depended on CircularMenu to initialize them properly. Now the tooltip will work with any button or control node. Also, the CircularButton works on its own, as it should: it doesn't need the menu to pass polar coordinates anymore.

Add centered layout (centered around the Y axis)
Add offset for the entire layout

Added contextual menu scene

This adds the base for a contextual menu. It has to be extended to work both in combat and in other contexts (i.e. open the inventory and what not)

Still does not close #65 because it's not working on the combat scene yet

I renamed `encounter` to `encountered_enemies` and used a few new signals to
remove a `get_parent` call, etc.

* Added monster drops

Monsters can now be configured to drop items based on a resource (MonsterDrops.gd).
The usability is not the greatest, but that's due to not being able to export custom types. 
There were two possible approaches that I saw:
1. An `Array` holding dictionaries for each item that can be dropped along with the data needed for the drop behavior.
2.  Create a custom resource that would encapsulate all the data for the items that can be dropped from a monster: The item itself, min and max quantities, and the chance. 

I decided to go with the first one.

ps: The items are _NOT_ being added to the player's inventory . This is just the functionality needed for the monsters to start dropping items.

Closes #59

* Embedded drops array to battler template, fixed code issues

Use class_name for pawns and derivatives
Make it so followers are not registered in the grid so they don't collide with the player's pawn
Rename classes to Pawn* to make it clear they're related to the map/grid

Added CoC based on GNU Kind Communications Guidelines