Move colors enumerations to a separate file

Named colors.h.

Also add some comments to the enumerations.
Move obsolete MAX_COLOR_SCHEMES macro

From the color_scheme.h file to the vifmrc-converter.c, since it's the
last file that still uses MAX_COLOR_SCHEMES macro.
Add initial version of color manager

Also were added tests and call to initialization of color manager at
startup.
Add parsing implementation for non-wrapped preview

This implementation is just a beginning.  Most of introduced functions
need to be rewritten.  Support for wrapped preview and explorer mode is
yet to come.
Small code enhancements

Introduce print_line_esc() function to reduce code duplication.
Introduce max_width and max_height local constants to ease code reading.
Define a macro with column of quick view content

To omit magic numbers.
Fix displaying of utf8 characters in quickview

This time add some tests.
Add parsing implementation for wrapped preview
Replace two display functions with one

It combines both wrapped and non-wrapped modes.  It's possible, since
non-wrapped mode is a special case of wrapped mode.
Refine view_file() function

Extract two more functions out of it to make it much more readable.
Remove remove_eol() function of file_streams.c

It's not used anymore.
Introduce escape parser state structure
Refine escape sequence parser

Extract different parts to functions, replace long series of if-else-if
with a switch statement.
Use is_null_or_empty() function where appropriate
Make pick_vi() of modes/view.c more universal
Introduce redraw() function to modes/view.c

Just includes two lines that were repeated three times in the
view_redraw() function.
Move escape sequences related things to escape.c

It was extracted from quickview.c.
Use esc_ prefix for all public escape.c functions
Add esc_remove() function to escape.c

It returns a copy of string with all escape sequences removed.

Also esc_str_overhead() function was moved in the files.
Make explore mode handle escape sequences

Highlighting of search results doesn't work properly yet.