adds method interrupt_if_install_required to WikkaWebService and unit test
update wikka.php to include install interrupt; stubs out InstallHandler
completes intro stage for InstallHandler
sets version to 2.0 to ease installer dev
updates template to use Bootstrap 3 styling
adds override stylesheet for install
cleans up InstallHandler intro stage; adds permission warning
adds database section to InstallHandler form
adds helper function build_input_form_group to InstallHandler and refactors stage states
adds migrations file for install process