Added first readme for jCoAP Proxy; added compiled jars; fixed accept option issue, fixed statistic resource implementation

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fixed jcoap-example & jcoap-applications classpath to remain at Java 1.6
removed outdated gradle build to maintain consistency
added license information to maven pom of jcoap
removed coapcache test implementation

added CoapClientChannel.createRequest() signature to consume all mandatory information required for a sound request message.
Thus it is not possible to create an unfinished request with this call.
old createRequest(reliable?, CoapRequestCode); is marked as deprecated as it allows creating unsound requests.
reordered the parameters for better human readability

Added Method signature CoapMessage.setPayload(CoapData data) to soundly set the payload including corresponding media type.

Changed the CoapResource interface by adding functions to add and remove arbitrary tags
Changed BasicCoapResource to implement the interface changes. If a resource is set to be observeble a tag(flag) "obs" is added automatically
Changed the core resource to append arbitrary tags to the resources

further classes have been adapted to the changes mentioned above

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class path was missing direct reference to log4j which caused class not found exception when running on remote devices via eclipse

jCoAP crashed when multicast was not allowed on a machine: Added Exception Handler, instead of a system failure, a warning is shown that jCoAP runs without multicast support
fixed test setup: some static modifiers crashed the test and thus the build
updated jcoap-core version to 1.1.2
updated dependencies in all projects
renamed all maven artifacts with a prefix "jcoap-" as otherwise generated jars are not identified with jcoap
removed all snapshot endings in version numbers
set all .settings to be ignored not just in root

rename maven artifacts for clarification (now: org.ws4d.jcoap.core, org.ws4d.jcoap.examples, org.ws4d.jcoap.proxy)
jcoap.core: removed jUnit4 dependency from classpath; was already part of maven build
jcoap.examples: removed jcoap.core project dependency from classpath; added dependency to maven build