add keymap C-c _ and C-c : for heading and separator insertion, respectively
* lisp/org-table.el (org-table-insert-line): Change function to
take character as parameter.
* lisp/org-table.el (org-table-insert-hhline,
org-table-insert-hcline): New functions to insert heading and
calculation separator using `org-table-insert-line'.
* lisp/org.el (org-ctrl-c-underscore, org-ctrl-c-colon): Add function
for defkey and document the keydef.
C-c ~ is already used for table.el conversion, maybe change this to
some other key and use C-c ~ for headers.