Transfer trusted certs during bootstrap
add trusted_certs_dir to generated config
Use :trusted_certs_dir from Chef::Config, only grab .crt and .pem files
Fetch certs in bootstrap_context.rb, not in templates to avoid copypasta.
Look for certs only if :trusted_certs_dir is not nil
Stub reading of validation key
reliably stub cert transfer tests
Update for trusted cert transfer during bootstrap.
[master/12] Fix whyrun_safe_ruby_block regression

`whyrun_safe_ruby_block` broke in the 11 changes.

Forward port of #2021
Detect invalid X509 certificates.
Refactor X509 certificate validation and debugging.
Use stronger wording in warn message
rebase
unit test for secret file discovery
add CHANGELOG for pr/1577
Merge pull request #2031 from opscode/lcg/1577

Rebase and ChangeLog for PR 1577
fix CHEF-4933
rewrite in the style of remote_directory
fix bug
refactering