Allow transparet background in WidgetScrollBox

Transparency is true by default. Please note that when rendering other
widgets inside of a transparent WidgetScrollBox, the `render_to_alpha`
flag must be set to true for those widgets.
Merge pull request #564 from dorkster/bugfixes

Allow transparet background in WidgetScrollBox
Don't process expired hazards

Fixes a segfault caused by expired hazards (aka hazards that have
traveled outside the map).
Remove unneeded function calls
Merge pull request #570 from igorko/master

Fix false positive error messages from console
Added titles and hero names to translatable strings.
Updated the Galician (gl) translation.
Add --game command line flag

This allows for the creation/search of directories under a single
"flare" directory. For example, if we launch Flare with `flare
--game=wandercall`: config files will be in
`$CONFIG_DIR/flare/wandercall/`; saves will be in
`$LOCAL_DATA_DIR/flare/wandercall/`; and game data (mods folder) will be
in `$DATA_DIR/flare/wandercall/`.

If the flag is not set, we fall back to the current directory.
Change default data directory in CMakeLists.txt
Rename --game_data flag to --data_path
Don't fall back when --game is omitted
Allow the use of locally installed mods

We can now load mods from the same place we store save games. So if
saves are stored at `$HOME/.local/share/flare/wandercall/`, we can put
mods in `$HOME/.local/share/flare/wandercall/mods/`.
Rename ENGINE_FOLDER to GAME_FOLDER
Merge pull request #573 from Gallaecio/gl

Updated the Galician (gl) translation.
Fix minimap position
Handle "divide on zero" exception.
Fix magic numbers
Merge pull request #571 from stefanbeller/master

Add title and names of heros to translatable strings.
Merge pull request #576 from igorko/bugfixes

Handle "divide on zero" exception.
Merge pull request #577 from igorko/master

Fix magic numbers