Added few scalar functions

I have renamed sign to signum because in scala.math this function has signum name
It fails on heap test
[info] Test com.typesafe.slick.testkit.tests.RelationalScalarFunctionTest.test[heap] started
[error] Test com.typesafe.slick.testkit.tests.RelationalScalarFunctionTest.test[heap] failed: scala.MatchError: Function exp (of class scala.slick.ast.Library$JdbcFunction)
[error]     at scala.slick.memory.QueryInterpreter.evalFunction(QueryInterpreter.scala:316)
[error]     at scala.slick.memory.QueryInterpreter.run(QueryInterpreter.scala:306)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef$$anon$3.run(MemoryProfile.scala:50)
[error]     at scala.slick.memory.QueryInterpreter$$anonfun$5.apply(QueryInterpreter.scala:50)
[error]     at scala.slick.memory.QueryInterpreter$$anonfun$5.apply(QueryInterpreter.scala:50)
[error]     at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
[error]     at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
[error]     at scala.collection.Iterator$class.foreach(Iterator.scala:727)
[error]     at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
[error]     at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
[error]     at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
[error]     at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
[error]     at scala.collection.AbstractTraversable.map(Traversable.scala:105)
[error]     at scala.slick.memory.QueryInterpreter.run(QueryInterpreter.scala:50)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef$$anon$3.run(MemoryProfile.scala:50)
[error]     at scala.slick.memory.QueryInterpreter.run(QueryInterpreter.scala:51)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef$$anon$3.run(MemoryProfile.scala:50)
[error]     at scala.slick.memory.QueryInterpreter$$anonfun$7.apply(QueryInterpreter.scala:61)
[error]     at scala.slick.memory.QueryInterpreter$$anonfun$7.apply(QueryInterpreter.scala:59)
[error]     at scala.collection.Iterator$class.foreach(Iterator.scala:727)
[error]     at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
[error]     at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
[error]     at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
[error]     at scala.slick.memory.QueryInterpreter.run(QueryInterpreter.scala:59)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef$$anon$3.run(MemoryProfile.scala:50)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef$$anon$3.run(MemoryProfile.scala:46)
[error]     at scala.slick.memory.QueryInterpreter.run(QueryInterpreter.scala:146)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef$$anon$3.run(MemoryProfile.scala:50)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef.run(MemoryProfile.scala:53)
[error]     at scala.slick.memory.MemoryProfile$QueryExecutorDef.run(MemoryProfile.scala:41)
[error]     at com.typesafe.slick.testkit.tests.RelationalScalarFunctionTest.checkWithPrecise$1(RelationalScalarFunctionTest.scala:13)
[error]     at com.typesafe.slick.testkit.tests.RelationalScalarFunctionTest.test(RelationalScalarFunctionTest.scala:58)
[error]     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error]     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
[error]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error]     at java.lang.reflect.Method.invoke(Method.java:606)
[error]     at com.typesafe.slick.testkit.util.Testkit$$anonfun$runChildren$2.apply(Testkit.scala:49)
[error]     at com.typesafe.slick.testkit.util.Testkit$$anonfun$runChildren$2.apply(Testkit.scala:40)
[error]     at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:772)
[error]     at scala.collection.Iterator$class.foreach(Iterator.scala:727)
[error]     at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
[error]     at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
[error]     at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
[error]     at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:771)
[error]     at com.typesafe.slick.testkit.util.Testkit.runChildren(Testkit.scala:40)
[error]     at com.typesafe.slick.testkit.util.SimpleParentRunner.run(SimpleParentRunner.scala:56)
[error]     ...