Allow for use of either 128x64 or 128x32 displays

Support for custom font table look-up function

Fix platforms in library.json

fix typo in integer type (causes compile error)

`warning: narrowing conversion of '128' from 'int' to 'const char' inside { } [-Wnarrowing]`

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.

Also use closer indicator spacing when using indicators on left or
right of screen with less than 64 height.

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