Bugfix: check target-file arg is non-nil before checking filename

Altered items:
org-dotemacs-load-file
Add code for error-handling and command-line args

New code to choose how org-dotemacs-load-blocks handles errors,
and variables for controlling behaviour from command line.

Altered items:
org-dotemacs-error-handling, org-dotemacs-tag-match,
org-dotemacs-load-file, org-dotemacs-load-blocks
Fix code for handling command line arguments

Also alter messages to begin with "org-dotemacs: " so they are easy to find in the
*Messages* buffer, and fix org-dotemacs-load-blocks to be defun* instead of just defun.

Altered items:

org-dotemacs-load-blocks
New customization option org-dotemacs-default-file

Altered items:
org-dotemacs-default-file, org-dotemacs-load-file
Move org-dotemacs-load-file to end of file
New command org-dotemacs-load-default

Convenience command that doesn't prompt for any filenames.

Altered items:
org-dotemacs-load-default
Alter org-dotemacs-load-default

Set default value of match arg to "" (which matches all tags)

Altered items:
org-dotemacs-load-default
Bugfix: org-dotemacs-load-default

Add arguments to call to org-dotemacs-load-file

Altered items:
org-dotemacs-load-default
Use current-kill instead of kill-ring in org-dotemacs-extract subtrees

Altered items:
org-dotemacs-extract-subtrees
Alter org-dotemacs-load-blocks to use properties

Use org properties to set block name and dependencies
Block specific name gets priority, block specific dependencies
are added to property dependencies.

Altered items:
org-dotemacs-load-blocks
Bugfix: check if unmet-dependencies is empty in org-dotemacs-load-blocks

Before assuming all blocks were successful need to check that both unmet-dependencies
and unevaluated-blocks are nil

Altered items:
org-dotemacs-load-blocks
Bugfix: org-dotemacs-load-blocks only print messages if necessary

Check that evaluated-blocks, unevaluated-blocks and unmet-dependencies are
non-nil before printing associated messages.
Also add org-dotemacs to beginning of all messages.

Altered items:
org-dotemacs-load-blocks, org-dotemacs-load-file
Make org-dotemacs-error-handling customizable

Also add ERROR-HANDLING arg to org-dotemacs-load-file,
move code for handling command line arguments to the end of the file
and added more documentation.

Altered items:
org-dotemacs-error-handling, org-dotemacs-load-file
Change customization group to org-dotemacs
Update documentation

Also change name of errorhandling arg to error-handling

Altered items:
org-dotemacs-load-blocks
Update README.md using mdr-generate command
Add to documentation

Note about columns view
Add exclude-todo-state & include-todo-state args to org-dotemacs-extract-subtrees

Altered items:
org-dotemacs-extract-subtrees
Add org-dotemacs-include-todo & org-dotemacs-exclude-todo options

Altered items:
org-dotemacs-include-todo, org-dotemacs-exclude-todo
Bugfix: change defun to defun* in org-dotemacs-extract-subtrees

Altered items:
org-dotemacs-extract-subtrees, org-dotemacs-load-blocks