ARQGRA-262: race condition fixed

The bug has been caused by the following scenario:
1. javascript extension is requested
2. executor checks whether the extension is installed -> it isn't
3. executor installs the extension
4. again, executor checks whether the extension is installed -> it is
5. new page is loaded (all installed extensions are dropped)
6. the extension is invoked -> but it isn't installed -> FAIL

The invocation process has been refactored to avoid this type of race condition:
1. javascript extension is requested
2. try to invoke the extension
3. if the invocation throws an exception, install the extension and repeat the invocation

New configuration property 'javascriptInstallationLimit' has been introduced.
ARQGRA-250: introduced value() shortcut in fluent API
fixed failing javascript tests