Add snippet for the VHDL component declaration.
Add snippet for the VHDL component instantiation.
Use “negative-logic” reset by default in sync process snippet

The default setup for the synchronous process reset is changed to use the
“negative-logic” reset which is more commonly used.
Refactor sync process snippet.

 * The comma separator in the sensitivity list is now only generated when a
   reset signal is defined
 * Indentation of the synchronous block restored.
 * Removed unnecessary brackets.
Make the sync process id label optional

The synchronous process may not be labeled (removing the default label).
When the label is not defined, the associated code (i.e. colon) is removed.

The code generated by the snippet now contains the block name as closure label
instead of a trailing comment.
It is supported by the VHDL grammar and unlike the trailing comments, there’s no
risk of become outdated due to a block renaming, which leads to misleading
comments.
Merge remote-tracking branch 'origin/new_snippets'
Fix labels in vhdl snippets.

 -The closure labels are now included as VHDL code instead of trailing
  comments.
 -If a label is not defined, the associated code (i.e. colon) is not
  generated.
Remove unnecesary blankspaces