vifm: Add alt file opening, option cycling mappings

Added cycling through (command mode) options with C-p/C-n since
I am used to doing this.

Added a quick short mapping to `o` to show all file openers
defined for the current file and be able to select one.

terminal/.config/vifm/vifmrc

@@ -1,4 +1,4 @@
-" vim: filetype=vifm : set foldmethod=marker foldlevel=0 nomodeline:
+" vim: filetype=vim : set foldmethod=marker foldlevel=0 nomodeline:
 " Sample configuration file for vifm (last updated: 20 July, 2018)
 " You can edit this file by hand.
 " The " character at the beginning of a line comments out the line.
@@ -227,12 +227,15 @@ nmap Q :q<cr>
 " Sample mappings
 " for now they use space for my leader key - so we can't switch panels with
 " space, use tab for that
-"nnoremap <space> <nop>
-nnoremap <space><space> <space>
+nmap <space> <nop>
+nnoremap <space><space> <nop>
 
 " switch pane with tab, like cpoption did
 nnoremap <tab> <c-w>w
 
+" scroll through command-line options with C-p/C-n
+cnoremap <c-p> <s-tab>
+cnoremap <c-n> <tab>
 
 " Start shell in current directory
 nnoremap s :shell<cr>
@@ -274,6 +277,9 @@ nnoremap cW cw
 " esc quits out of preview mode (it does in vim, why not here?)
 qnoremap <esc> q
 
+" quickly show alternative file opening applications
+nnoremap o :file <tab>
+
 " Select file and jump in the indicated direction
 nnoremap J tj
 nnoremap K tk
@@ -361,12 +367,13 @@ source $VIFM/favicons.vifm
 " program.
 
 " Pdf
-filextype *.pdf
+filextype <application/pdf>,*.pdf
         \ { view as rich file }
         \ sioyek %c %i, zathura %c %i &, apvlv %c, xpdf %c,
         \ { edit text content }
         \ pdftotext -nopgbrk %c - | nvim
-fileviewer *.pdf pdftotext -nopgbrk %c -
+filextype <application/pdf>,*.pdf
+        \ pdftotext -nopgbrk %c -
 
 " PostScript
 filextype *.ps,*.eps,*.ps.gz
@@ -458,6 +465,11 @@ filextype *.ora
         \ {Edit in MyPaint}
         \ mypaint %f,
 
+" OpenRaster
+filetype *.sqlite,*.db
+        \ {Edit in sqlite3}
+        \ sqlite3 %f,
+
 " tabular data
 filextype *.csv
         \ {Open with visidata}