[manpages] Rewrite man pages in a simpler text format.

Makefile still needs work, but I wanted to commit to save progress.

man8/thin_delta.txt

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+NAME
+  thin_delta - Print the differences in the mappings between two thin devices.
+
+SYNOPSIS
+  thin_delta [options] {device|file}
+
+DESCRIPTION
+  thin_delta allows you to compare the mappings in two thin volumes (snapshots
+  allow common blocks between thin volumes).
+
+  This tool cannot be run on live metadata unless the --metadata-snap option is
+  used.
+
+OPTIONS
+  --thin1, --snap1 {natural}	The numeric identifier for the first thin volume to diff.
+  --thin2, --snap2 {natural}	The numeric identifier for the second thin volume to diff.
+  --metadata-snap [block nr]	Use a metadata snapshot.
+
+    If you want to get information out of a live pool then you will need to
+    take a metadata snapshot and use this switch.  In order for the information
+    to be meaningful, you need to ensure the thin volumes you're examining are
+    not changing (ie, do not activate those thins).
+
+  --verbose	Provide extra information on the mappings.
+  -h, --help		Print help and exit.
+  -V, --version		Output version information and exit.
+
+SEE ALSO
+  thin_dump(8), thin_repair(8), thin_restore(8), thin_rmap(8), thin_metadata_size(8)
+
+AUTHOR
+  Joe Thornber <ejt@redhat.com>, Heinz Mauelshagen <heinzm@redhat.com>
+