Repainted arrow and scaled it to different sizes for different densities
Added arrow.png for different densities
Implemented the rotation arrows with paths instead of using a bitmap
Removed now uneccessary drawables
Added .gitignore
Introduced constants for arrow dimensions and made them density dependent
Merge pull request #163 from Catrobat/Issue155_ToolArrowsZoom

Issue155 tool arrows zoom
Implementation: @dladenhauf [DL]
Acceptance: @galstc05 [SG]