As per the feedback at https://github.com/google/fscrypt/issues/115
where users didn't understand that the recovery passphrase is important,
restore the original behavior where recovery passphrase generation
happens automatically without a prompt.  This applies to the case where
'fscrypt encrypt' is using a login protector on a non-root filesystem.

However, leave the --no-recovery option so that the recovery passphrase
can still be disabled if the user really wants to.  Also, clarify the
information provided about the recovery passphrase.

Update https://github.com/google/fscrypt/issues/115

Resolves https://github.com/google/fscrypt/issues/305

Update https://github.com/google/fscrypt/issues/115

Capitalize the first word only, and don't use periods.

Resolves https://github.com/google/fscrypt/issues/51
Resolves https://github.com/google/fscrypt/issues/115

A lot of people are already using fscrypt, so in practice we haven't
been breaking backwards compatibility and aren't going to.  Just remove
the scary-sounding "Note about stability".

These would still be nice to add.  However, the mention of them in the
README is misleading because people reading it might come away with the
impression that there is currently no way to back up fscrypt metadata or
to recover directories -- which isn't true.  (The fscrypt metadata is
just a directory which can be backed up like any other directory.  And
'fscrypt encrypt' already offers to generate a recovery passphrase when
the directory and protector are on different filesystems.)

Just remove this note; it doesn't really add any value.

Update https://github.com/google/fscrypt/issues/305

Clarify some of the troubleshooting documentation.