Username can be edited by double clicking on text, added global user profile menu action in user info widget

Link opening only works on Linux for now.

See https://github.com/matrix-org/matrix-doc/pull/2312

* add username error label, add word wrapping for error labels

* make lint

* last commits

* remove font, and remove some lambdas

* add QRegularExpression for regex

* improve review things

* add isModified() for checkFields()

* add check isModified() for  all fields in checkFields

* Update src/RegisterPage.cpp

Co-authored-by: DeepBlueV7.X <nicolas.werner@hotmail.de>

* remove emit call for showError

Co-authored-by: DeepBlueV7.X <nicolas.werner@hotmail.de>

move error_matrixid label below matrixid input, made hide/show for the label, made red underline for invalid input, add to TextField class isValid() setValid() for custom validation

There is no need to iterate over a list, flags can be applied and stored
simultaneously.