refacto/feat: better handling of parser updates

features:
- node_movement is moving between scopes.
- add selection initialization from normal mode
- add a decremental selection

improvements:
- attach to buffer to run tree parsing on change
- run state update on CursorMoved
- the buffer state is:
```
{
  cursor_pos = { row=row, col=col },
  current_node = node_under_cursor,
  selection = {
      range = nil, -- activates when starting a selection
      nodes = {} -- filling up when starting an incremental selection
  },
  parser = parser, -- parser for current buffer
}
```
- refacto all the modules reliant on parsing the tree, update the current nodes, get the current nodes...

fixes:
- fix has_parser to look for .so libraries
- fix should select the whole file when selection root in selection

doc/nvim-treesitter.txt

@@ -31,25 +31,27 @@ By default, everything is disabled. To enable support for features, in your `ini
   lua <<EOF
   require'nvim-treesitter.configs'.setup {
     highlight = {
-        enable = true,                 -- false will disable the whole extension
-        disable = { 'c', 'rust' },     -- list of language that will be disabled
+        enable = true,                    -- false will disable the whole extension
+        disable = { 'c', 'rust' },        -- list of language that will be disabled
     },
-    incremental_selection = {             -- this enables incremental selection
+    incremental_selection = {
         enable = true,
         disable = { 'cpp', 'lua' },
         keymaps = {                       -- mappings for incremental selection (visual mappings)
-          node_incremental = "<leader>e", -- "grn" by default,
-          scope_incremental = "<leader>f" -- "grc" by default
+          init_selection = 'gnn',         -- maps in normal mode to init the node/scope selection
+          node_incremental = "grn",       -- increment to the upper named parent
+          scope_incremental = "grc",      -- increment to the upper scope (as defined in locals.scm)
+          scope_decremental = "grm",      -- decrement to the previous scope
         }
     },
     node_movement = {                           -- this cursor movement in node hierachy
         enable = true,
         disable = { 'cpp', 'rust' },
-        keymaps = {                       -- mappings for node movement (normal mappings)
-          move_up = "<a-k>",              -- default is to move with alt key hold
-          move_down = "<a-j>",
-          move_left = "<a-h>",
-          move_right = "<a-l>",
+        keymaps = {                       -- mappings for scope movement
+          parent_scope = "<a-k>",         -- default is to move with alt key hold
+          child_scope = "<a-j>",
+          next_scope = "<a-h>",
+          previous_scope = "<a-l>",
         }
     },
     ensure_installed = 'all' -- one of 'all', 'language', or a list of languages