Use tpm2-software TSS implementation, and xaptum-tpm's nvram utils

[zanebeckwith]

This PR builds this project against the tpm2-software implementation of the TPM TSS2 (rather than the xaptum-tpm implementation). As part of this, this also removes the implementation of TPM NVRAM utilities from this library and uses the (essentially identical) ones from xaptum-tpm (and also the definitions of certain constant handle values, which were also duplicated between here and xaptum-tpm).

This includes:

• Building a local installation of the tpm2-software TSS in Travis-CI builds
• Building the xtt project against this new TSS
  • In addition to the CMake changes, this requires a few changes to type names in xtt (e.g. TPM_HANDLE -> TPM2_HANDLE)
  • The new cmake/ scripts are copies from the same ones used in xaptum-tpm and ecdaa, for finding the TSS2 libraries
• Building xtt against v1.0.0 of ecdaa
  • Because this new ecdaa also builds against the tpm2-software TSS
• Removing the tpm/[nvram,handles] files
• Updating some names of nvram-related things for the xaptum-tpm version (e.g. XTT_ prefix becomes XTPM_ prefix)

NOTE: This currently hardcodes the xaptum-tpm version installed in Travis to a temporary branch that incorporates multiple feature branches (that are currently under review). Once those xaptum-tpm PRs are merged, and before this PR is, I'll change that to build a master branch xaptum-tpm.

[zanebeckwith]

Now that the xaptum-tpm changes have been merged, and a new release cut, I've updated this branch to use the new xaptum-tpm release