separate vim config from nvim config again and simplify it

Separating vim's config from neovim's config simplifies the deployment
of lua for neovim's configuration. At the same time, clean up current
neovim config by removing all outdated options and options with equal or
even better defaults. Furthermore, the 'old' vim configuration should be
kept as-is to ensure compability with older systems if needed.

config/nvim/general.vim

@@ -1,9 +1,5 @@
-" drop vi-compatibility
-set nocompatible
 " disable autocmd
 set secure
-" use utf8 only
-set encoding=utf8
 
 " file/directory matching
 set wildmode=list:longest,full
@@ -19,24 +15,6 @@ set history=1000
 " increase count of possible undos
 set undolevels=1000
 
-" encrypt buffers when saved to files
-if exists('+cryptmethod')
-	set cryptmethod=blowfish
-endif
-
-" enable fast terminal for tmux but not for ssh connection
-if &term =~# '^screen' && !exists('SSH_CONNECTION')
-	set ttyfast
-endif
-
-" enable automatic file detection, plugin and indention support
-if has('autocmd')
-	filetype plugin indent on
-endif
-
-" use utf8 encoding for all files and recognize latin1
-set fileencodings=utf-8,latin1
-
 " use unix line-endings and recognize dos endings
 set fileformats=unix,dos
 
@@ -114,7 +92,7 @@ set number
 " show cursor position all the time
 set ruler
 
-" show tabs all the time
+" show vim tabs all the time
 set showtabline=2
 
 " show currently typed command
@@ -134,7 +112,6 @@ set updatetime=300
 set timeoutlen=500
 
 " copy paste between vim and everything else
-" TODO: check whether the 'plus' suffix works with plain vim
 set clipboard=unnamedplus
 
 " Misc