Remove theme-compiler and replace with external vaadin-sass-compiler

* Moves CompileTheme from the theme-compiler to buildhelpers
* Refactors CompileTheme to get the Vaadin version on the command line
  instead of using the Version class found in vaadin-shared
* Refactors build scripts to pass the version number on the command line
  when running CompileTheme
* Removes the theme-compiler module/project/whatchamacallit
* Replaces the theme-compiler dependency with vaadin-sass-compiler 0.9.0
  from maven

Change-Id: I4f98d15b60e18a826bf264eb55d12b3e736e8e54