Added Hash and Encryption support in Web component

Here I integrated essential cryptography utilities into Web component to secure personal data for local and cloud use.
Supported utilities:
+ Hashing: md5, sha-1, sha-256, sha-384, sha-512
+ HMAC: hmacmd5, hmacsha1, hmacsha256, hmacsha384, hmacsha512
+ AES-256 symmetric encryption/decryption
+ RSA asymmetric encryption/decryption
+ DSA signature/verification

For details, please refer to the proposal: https://docs.google.com/document/d/1XuiftqF1hICxZebNpay2mF6PKQXi3c8azh_89iZZ59M/edit?usp=sharing

Try it on http://ai2-enc.appspot.com with its [Companion app](https://www.google.com/url?q=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F0B6pgfXvNtaFybVVtM3pQeXAtQ1U%2Fedit%3Fusp%3Dsharing)

Demo projects: [HashEncDemo.aia](https://www.google.com/url?q=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F0B6pgfXvNtaFyVXE5OWFGRUJrQk0%2Fedit%3Fusp%3Dsharing), [FileEncryptDemo.aia](https://www.google.com/url?q=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F0B6pgfXvNtaFyWVZFVDVIX0RPQ2M%2Fedit%3Fusp%3Dsharing), [DsaDemo.aia](https://www.google.com/url?q=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F0B6pgfXvNtaFyVVUyU3lDWmR3d2s%2Fedit%3Fusp%3Dsharing)

Post: https://groups.google.com/forum/#!topic/app-inventor-open-source-dev/nKlVsW_JR8c