Implement the deposit side of Voting Pools

This contains the APIs to create and retrieve Voting Pools and Series (with
public/private keys) from a walletdb namespace, plus the generation of deposit
addresses (using m-of-n multi-sig P2SH scripts according to the series
configuration).
Switch to new subrepo import paths.
Remove Go 1.2 and add release to TravisCI builds.

Our policy is to only ensure the code compiles for the latest Go release
minus one version.  Since Go 1.4 has now been released, this commit
updates TravisCI to remove Go 1.2 from the build matrix.  While here, add
release to the matrix which should have been there before anyways.
Move keystore to legacy directory.
Switch to new waddrmgr package

This commit converts the wallet to use the new secure hierarchical
deterministic wallet address manager package.

The following is an overview of modified functionality:

- The wallet must now be created before starting the executable
- A new flag --create has been added to create the new wallet using wizard
  style question and answer prompts
- Starting the process without an existing wallet will instruct now
  display a message to run it with --create
- Providing the --create flag with an existing wallet will simply show an
  error and return
Add conversion from legacy txstore if it exists.
Integrate walletdb and updated waddrmgr.

This commit converts the wallet to use the new walletdb package as well as
the updated version of the secure hierarchical deterministic wallet
address manager which uses the new namespace feature provided by waleltdb.
Address some review items.

- Distinguish between missing address and database error
- Wrap help text for wallet generation seed
- Don't rescan if there are no addresses
- Update --create message for legacy wallet import
Turn echo off when reading passwords
Allow  main waddrmgr test to run in parallel.
Switch to new subrepo import paths.