[#50155187]  Update model to allow for one piece of art to have multiple categories. Also updated the upload to include all categories separated by a "," in the "category" paramter
warning cleanup
Merge remote-tracking branch 'origin/detailviewupdate' into multi-categories
[#50333201][#48968545] Date picker fixed. Took Category out of map callout and list view rows
Merge branch 'multi-categories' of https://github.com/ArtAround/artaround-ios into multi-categories
Merge remote-tracking branch 'origin/multi-categories' into detailviewupdate

Conflicts:
	src/ArtAround.xcodeproj/project.pbxproj
	src/ArtAround/Classes/AppDelegate/ArtAroundAppDelegate.m
	src/ArtAround/Classes/Views&Controllers/AddArtViewController.h
	src/ArtAround/Classes/Views&Controllers/AddArtViewController.m
	src/ArtAround/Classes/Views&Controllers/ArtListViewCell.m
	src/ArtAround/Classes/Views&Controllers/CalloutAnnotationView.m
updated model version
Updated category filtering