Merge pull request #24 from ferstaberinde/dev

Dev
Added add button,added slots to mobile, fixed icons not appearing in mobile mode.
Merge branch 'master' of github.com:ferstaberinde/FAMDB
Removed placeholder.
Table is now sorted alphabetically by default
Fixed table-header issue in mobile display
Fixed slots accepting NaN and updated error messages.
Mission name now must contain at least one character and must not begin a whitespace.
Improved checks for missionDescription and missionNotes to not accept blank-only input.
Toggleable author selection for add page
* authors are now selected from existing authors by default (when adding)
* new file: common.js (moved missionSaveError & getMissionAuthor here)

ToDo:
* Allow selection of > 1 author
* The plus symbol's size & positioning needs to be tweaked a bit; maybe just use a normal "+" instead?