Add Instant filter to the "Recent log messages" (admin/reports/dblog) page

We need to replace the core filter thingy with instantfilter and provide the "Type" & "Severity" options as two sets of checkboxes.

PS: please update the project's page to include #1262034: Add Instant filter to admin/reports/updates (in the list of forms instantfilter is implemented), perhaps this issue here if you decide to accept the feature request.