Add linking with OpenSSL to build files

Flag --with-rsa allows to build the project with RSA-SHA1 signature
method. OpenSSL must be installed. Build script tries to find OpenSSL
library file and include directory. If it fails, these paths must be explicitly
specified with --openssl-libpath and --openssl-includepath build variables.
Add sha1 algorithm for use with RSA-SHA1
Add implementation of RSA-SHA1 signature
Add tests for RSA-SHA1 signature
Make buildable under windows

paths changed to windows defaults
added necessary library
fixed openssl library name suffix
LIBS in test configuration reordered
Fix rsa under windows. Remove openssl linking to OAuth library.

applink.c included, it fixes OPENSSL_Uplink(10100000,08): no OPENSSL_Applink error
openssl linking to OAuth library isn't necessary, and sometimes will not work as might be expected
Merge pull request #3 from swat32exe/add-rsa-sha1-signature-melzas

Make buildable under windows
Use conditional compilation for openssl/applink.c and add libcrypto

openssl/applink.c is needed only on Windows
Fix possible memory leaks and change exception messages
Add Service tests for RSA-SHA1 signature
Fix path problem

now SCons should use system PATH variable
Fix HttpRequest includes
Merge pull request #4 from swat32exe/add-rsa-sha1-signature-melzas

Fix path problem and HttpRequest includes
Move RsaSignature sources to crypto/rsa
Add RsaSignatureWrapper to handle resources properly

Also replace PEM_read_PrivateKey with PEM_read_bio_PrivateKey. So now
RSA key can be passed as a string.
Merge pull request #27 from Melzas/add-rsa-sha1-signature

Add RSA-SHA1 signature