gui lists add callback for owner drawn items

allow the guts of gui_sync_list to be used with owner drawn items

WIP

printcell_helper--

goal: allow data to be displayed in a spreadsheet format  with an easy to use interface

printcell_set_columns(gui_synclist, title, icon)
 sets title and calculates cell widths
 each column is identified by '$' character
 ex 3 columns title = "Col1$Col2$Col3"
also accepts $*WIDTH$
 ex 3 columns varying width title = "$*64$Col1$*128$Col2$Col3
printcell_enable(gui_synclist, enable)
 sets the printcell function enabled

After setting the columns and enabling the printcell function
 items can be added to the list like normal
 column items are supplied delimited by '$'
 ex item = "Item1$item2$item3"
 they will be placed in cells defined by set_columns and scroll if the cell is too small

--Fixed for 1 bit & 2 bit displays

Change-Id: I49bd7903005d7a54e93af4379b0cdea63c860656

apps/plugins/lib/SOURCES

@@ -14,6 +14,7 @@ rgb_hsv.c
 highscore.c
 simple_viewer.c
 display_text.c
+printcell_helper.c
 strncpy.c
 stdio_compat.c