Added string-split, added retry arg to org-dotemacs-load-blocks

Added retry arg org-dotemacs-load-blocks and altered behaviour
so that failed blocks will be retried. Also failed blocks divided
into blocks with errors and blocks with unmet dependencies.
Added string-split function (needed for checking dependencies).

Altered items:
string-split, org-dotemacs-load-file, org-dotemacs-load-blocks