Revert "Remove eval-and-replace"

This reverts commit 8fbfe2368cde1646bf60b9a07ac518dce61850ba.
Advice to call eval-and-replace on C-u C-u C-x C-e
Add a space when inserting timestamp
Set up boss speed agenda key
init-latex.el: Rewrite and delete "reinventing-the-wheel" functions