Word highlighting, lsp_signature, calendar and settings / keybindings

Plugins:

- added word highlighting plugin mywords
- added lsp_signature plugin to show parameter signature while typing a
  function call
- added calendar.vim
- added lush.nvim needed for some theme definitions, though not for the
  nice and current default lunaperche

Keybindings:

- <space>m[mrc] for mywords
- <C-W>0 and <C-W>1 for window close / make single
- <C-,> for lsp references
- <C-.> for lsp definitions

Options:

- highlight last search term
- add I to shortmess to start with an empty file instead of splash
  screen
- fzf uses default-title as theme
- fzf registered as vim.ui.select implementation
- which_key shows global definitions, too

lua/options.lua

@@ -27,7 +27,7 @@ vim.opt.showmode = false       -- we are experienced, wo don't need the "-- INSE
 
 -- Searching
 vim.opt.incsearch = true  -- search as characters are entered
-vim.opt.hlsearch = false  -- do not highlight matches
+vim.opt.hlsearch = true   -- do not highlight matches
 vim.opt.ignorecase = true -- ignore case in searches by default
 vim.opt.smartcase = true  -- but make it case sensitive if an uppercase is entered
 
@@ -45,3 +45,11 @@ vim.opt.wrap = false
 -- Spelling
 vim.opt.spell = true
 vim.opt.spelllang = "de,en"
+
+--------------------------------------------------
+--
+-- Other options
+--
+--------------------------------------------------
+
+vim.opt.shortmess = vim.opt.shortmess + 'I'