jrnl was missing ability to search in entry titles and message bodies.
This commit adds a '-search TEXT' option which, if specified, causes
jrnl to display only those entries which have 'TEXT' in either their
title or message body.
Specifying the '-search' option also implies that the compose mode
won't be used.
Fixes#384.
Previously, if a user forgot the exact name of a journal, they could check the configuration file to retrieve this information. This patch adds support for performing this task using the jrnl interface.
The newly added '-ls' option retrieves the available journals from the jrnl configuration files and displays each journal name on a separate line.
This patch also updates the jrnl help display and the usage documentation to reflect these changes.
