Including weak PRP-PRF switching lemma, but not its strong version

Squashed commit of the following:

commit 005342f19a55b0ae01c88c0c729fdbad3f2519ff
Merge: 5407570b 7325ae6d
Author: François Dupressoir <fdupress@gmail.com>
Date:   Mon Feb 10 09:48:54 2020 +0000

    Merge branch '1.0' into deploy-simpler-rp

commit 5407570bbdeaee7b725f57fcdbbf764ff301ac9e
Author: François Dupressoir <fdupress@gmail.com>
Date:   Fri Jan 24 12:00:21 2020 +0000

    move towards merging PRF and RO

    also clean assignment notation

commit 65e0c4eb8c702729500148e34900dc5971e583a7
Author: François Dupressoir <fdupress@gmail.com>
Date:   Tue Jan 21 14:14:29 2020 +0000

    Integrate PRP-PRF switching lemma into PRP lib

    Not done for the strong version yet

commit 456a7c96e40fa6827d92fbc36d8cd75fdd8abab1
Author: François Dupressoir <fdupress@gmail.com>
Date:   Tue Jan 21 09:40:25 2020 +0000

    Simplifying the PRF interface

    No keys are needed for the ideal RP,
    The raw interface can be defined separately as needed.

commit e7dea73e6eae21f192efc45f42e9cdc9e5ec4eb8
Author: François Dupressoir <fdupress@gmail.com>
Date:   Tue Jan 21 09:19:04 2020 +0000

    Some nits

commit 8bb90549b6084ea8189e3a4067a155f977ccd34a
Author: François Dupressoir <fdupress@gmail.com>
Date:   Mon Jan 20 16:38:30 2020 +0000

    Cleanup PRP/PRF and PRP-PRF