fixed SimpleCurve
Added square
SimpleCurve is drawn by Bresenham function
added icons to toolbar
Fixed hole in drawing of simple curve
Drawing of a parallelogram
Drawing of rhombus
Merge commit '8e4269900f7b972b18ae242de198f6d1c9994dde'
Merge commit 'b8f1a0d5d51c71a0fcecdc06748c5e5eb2e91d0f'
Merge commit 'ebec999b61b4f8096228bf3991b3604f736d1316'
Merge commit 'a850a5362f49ca4b54dde0902e91d478e590f30e'
Merge branch 'in-progress' of https://github.com/didizlatkova/CornerStone
added diagonal options to square and rectangle