recieving start or request

This is necessary to support having a picker within QML.
Eventually, this should replace the existing widget-based one.

removed from:
 - emoji panel scrollbars
 - emoji category labels
 - splitter image handles
 - textfield setTextColor impl

small change to the category separator label for better contrast /
readability in dark mode.

removed setTextColor completely from TextField. Doesn't appear to be in
use anywhere, and focus going more toward qss themeing from qproperty
setting.

Respect system styling
Increase size of emojis (to remove empty space)
Add hover effect (partially adresses #41)
Less hardcoding of sizes
Use emoji font (color)

Restored the emoji picker, but it now falls back to the system
instead of forcing Emoji One.  The allows users to user the
picker for convenience, but doesn't enforce the emoji style on them.

This reverts commit 4b807229.

fixes #79

fixes #398

fixes #254
fixes #246

fixes #184
fixes #209

fixes #176