Disable ref counting of looped sounds

Fixes #760
Prevent getting stuck in a state when there is a missing animation

Fixes #769
added an option to hide labels and made some copy/paste cleaning
Fixes for option to show hotkey names

* Adds the checkbox to menus/config.txt
* WidgetCheckBox's constructor does a call to mods->locate() already, so
passing the results of mods->locate() to the constructor caused a crash
* Use the SHOW_HOTKEYS boolean in MenuActionBar instead of maintaining
a private variable
* Fix the spelling of placeLabeledCheckbox()
Merge pull request #1 from dorkster/showkeynames

 Fixes for option to show hotkey names
Merge pull request #764 from bmorel/show_keynames

Show keynames
added show_hotkeys_cb to tablist
Merge pull request #773 from bmorel/show_keynames

added show_hotkeys_cb to tablist
Merge pull request #771 from stefanbeller/master

Small code cleanups
Only reset block animation during takeHit()

Fixes #499

Bonus fix: Only roll once for poise chance
Merge pull request #774 from dorkster/double_cast_fix

Only reset block animation during takeHit()
Merge pull request #762 from dorkster/sound

Don't increase ref count when loading exisiting sounds
Merge pull request #770 from dorkster/animation

Prevent getting stuck in a state when there is a missing animation
Fix removing currency on death
Move the player's max level to a config file

Use `max_level=` in `engine/stats.txt`. The default is still 32.
Merge pull request #780 from dorkster/level_max

Move the player's max level to a config file
Improve error message for PowerManager loading powers
Define maximum level by xp table size instead of parameter
Merge pull request #775 from dorkster/bugfixes

 Fix removing currency on death
Merge pull request #782 from stefanbeller/improve_error_message

Improve error message for PowerManager loading powers