fix typo in integer type (causes compile error)

Closer to middle vertical align

Make OLEDDisplay.display() an abstract function

Implement setLoadingDrawFunction. Fixes #102

Without the `= 0` declaration, compiling with RTTI enabled fails.
See http://stackoverflow.com/a/307427/1880101 for an explanation.

Due to the 4px spacing, the indicators are a bit offset when adding them to LEFT or RIGHT sides of screen

Improve display performance of SH* drivers

Add SH1106Spi support

Fix internal black drawing

Add sample code

Make it possible to enable/disable all indicators

Fix a bug where multiline strings where not correctly centered

Improving rect drawing 

Fix calculation of final drawBit in drawVerticalLine