Allow configuring sign text/highlight group
Add variables 'g:qfx_hl_err', 'g:qfx_hl_warn', 'g:qfx_hl_info' and 'g:qfx_sign', allowing a user to configure the text character and highlight groups to use for qfx signs.
Add variables 'g:qfx_hl_err', 'g:qfx_hl_warn', 'g:qfx_hl_info' and 'g:qfx_sign', allowing a user to configure the text character and highlight groups to use for qfx signs.