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

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

man8/thin_ls.txt

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+NAME
+  thin_ls - List thin volumes within a pool.
+
+SYNOPSIS
+  thin_ls [options] {device|file}
+
+DESCRIPTION
+  thin_ls displays infomation about thin volumes in a pool.  Pass the metadata
+  device on the command line, not the pool device.
+
+  This tool cannot be run on live metadata unless the --metadata-snap
+  option is used.
+
+OPTIONS
+  -h, --help	Print help and exit.
+  -V, --version	Print version information and exit.
+  -o, --format	Give a comma separated list of fields to be output.
+
+    Valid fields are:
+      DEV, MAPPED_BLOCKS, EXCLUSIVE_BLOCKS, SHARED_BLOCKS, MAPPED_SECTORS,
+      EXCLUSIVE_SECTORS, SHARED_SECTORS, MAPPED_BYTES, EXCLUSIVE_BYTES,
+      SHARED_BYTES, MAPPED, EXCLUSIVE, SHARED, TRANSACTION, CREATE_TIME,
+      SNAP_TIME
+
+  --no-headers	Don't output headers.
+  -m, --metadata-snap	Use 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.
+
+SEE ALSO
+  thin_dump(8), thin_repair(8), thin_restore(8), thin_rmap(8), thin_trim(8),
+  thin_metadata_size(8)
+
+AUTHOR
+  Joe Thornber <ejt@redhat.com>