[Qt] RPC-Console: support nested commands and simple value queries

Commands can be executed with bracket syntax, example: `getwalletinfo()`.
Commands can be nested, example: `sendtoaddress(getnewaddress(), 10)`.
Simple queries are possible: `listunspent()[0][txid]`
Object values are accessed with a non-quoted string, example: [txid].

Fully backward compatible.
`generate 101` is identical to `generate(101)`
Result value queries indicated with `[]` require the new brackets syntax.
Comma as argument separator is now also possible: `sendtoaddress,<address>,<amount>`
Space as argument separator works also with the bracket syntax, example: `sendtoaddress(getnewaddress() 10)

No dept limitation, complex commands are possible:
`decoderawtransaction(getrawtransaction(getblock(getbestblockhash())[tx][0]))[vout][0][value]`

src/Makefile.qttest.include

@@ -1,13 +1,16 @@
 bin_PROGRAMS += qt/test/test_bitcoin-qt
 TESTS += qt/test/test_bitcoin-qt
 
-TEST_QT_MOC_CPP = qt/test/moc_uritests.cpp
+TEST_QT_MOC_CPP = \
+  qt/test/moc_rpcnestedtests.cpp \
+  qt/test/moc_uritests.cpp
 
 if ENABLE_WALLET
 TEST_QT_MOC_CPP += qt/test/moc_paymentservertests.cpp
 endif
 
 TEST_QT_H = \
+  qt/test/rpcnestedtests.h \
   qt/test/uritests.h \
   qt/test/paymentrequestdata.h \
   qt/test/paymentservertests.h
@@ -16,6 +19,7 @@ qt_test_test_bitcoin_qt_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(BITCOIN_
   $(QT_INCLUDES) $(QT_TEST_INCLUDES) $(PROTOBUF_CFLAGS)
 
 qt_test_test_bitcoin_qt_SOURCES = \
+  qt/test/rpcnestedtests.cpp \
   qt/test/test_main.cpp \
   qt/test/uritests.cpp \
   $(TEST_QT_H)