Added verilator_install to verisim makefile

Enable L2 TLB.

rocket-chip version 5d7a0e7c42278e523d68f980bf6d1c9674f6bdab

   * Remove MaxPermSize in java invocation (deprecated).
   * Rename project for better IntelliJ interaction.
   * Add .idea to gitignore so IntelliJ is ignored.

   * Add a faster init-submodule script (don't checkout/build riscv-gcc).
   * Add a script to build and install "lspike" -- a copy of spike that
      outputs the commit log to stderr.

Add an FAQ entry for setting up IntelliJ.

Add info about git submodule updates.

   * Bumps rocket-chip (for FIRRTL dedup update).

Requires a wipe and reclone of this repo for the new build.sbt to take hold.

Add more information on commit log generation.

Added an FAQ.