Extended widgets documentstion
refs #865
Added style information to ProgressBar
refs #865
Added docs to Header widgets
refs #865
Added docs to BackgroundImage
refs #865
Added docs to BackgroundPatter
Changed visibility of drawing handler
refs #865
Added docs to Button widget
Finished docs in pisak.widgets
refs #865
Fixed param listing by adding newlines
refs #865
Params docs in correct form in speller widgets
refs #864
Merge branch 'master' into doc-extend

Conflicts:
	pisak/widgets.py
Merge branch 'master' of github.com:BrainTech/pisak