The default keybindings now use StartOfText which moves the cursor
to the start of the text on the current line instead of the actual
start of the line (if the line begins with whitespace).
Fixes#1468
This change introduces header files for syntax files. The header
files only contain the filetype and detection info and can be
parsed much faster than parsing a full yaml file. To determine
which filetype a file is, only scanning the headers is necessary
and afterwards only one yaml file needs to be parsed. Use the
make_headers.go file to generate the header files. Micro expects
that all default syntax files will have header files and that
custom user syntax files may or may not have them. Resolving
includes within syntax has not yet been implemented. This
optimization improves startup time.
Ref #1427
