Introducing AbstractDiscriminator base class to avoid repeated start()/stop() implementation in each concrete Discriminator

LOGBACK-818: support for SSL-enabled socket appender and server

LOGBACK-796 RollingFileAppender should have error when File matches FileNamePattern

This commit modifies appenders.html to include information about
SSLSocketAppender, and adds a usingSSL.html (linked from the
relevant sections of appenders.html) that describes the SSL-related
configuration properties.

This commit adds the new appender and modifies the JoranConfigurator
to include rules for SSL configuration types.

This commit adds the new server and modifies SimpleSocketServer so
that its startup logic can also be applied to a SimpleSSLSocketServer.

This commit adds the new appender and modifies the
DefaultNestedComponent rules to include rules for SSL configuration
types.

In addition to the new base appender, this commit includes several
supporting classes that are used to create and configure an
SSLContext and all of its constituent components, and corresponding
unit tests and resources.

added another hsqldb file to gitignore

removed remaining call to new Socket() in reconnect (LOGBACK-815)

Missed one in previous commit.

Patch for LOGBACK-815, LOGBACK-816

update docs example Appender in appenders chapter at #WriteYourOwnAppender

fix for  form posts losing data

Minor improvements to CyclicBufferAppender, and tests

LOGBACK-805: DBAppender assumes that caller data is available on the event