Make InvalidIdentifier exception subclass of ExpressionError to report invalid attributes correctly

[Mingun]

The test

# expr_bad_id_inst_value.ksy: /instances/foo/value:
# 	error: invalid ID: 'BAD', expected /^[a-z][a-z0-9_]*$/
#
meta:
  id: expr_bad_id_inst_value
instances:
  foo:
    value: BAD

Fixes test which instead of reporting error shows this exception:

[info] - expr_bad_id_inst_value *** FAILED ***
[info]   io.kaitai.struct.format.InvalidIdentifier: invalid ID: 'BAD', expected /^[a-z][a-z0-9_]*$/
[info]   at io.kaitai.struct.format.Identifier$.checkIdentifier(Identifier.scala:52)
[info]   at io.kaitai.struct.format.InstanceIdentifier.<init>(Identifier.scala:113)
[info]   at io.kaitai.struct.ClassTypeProvider.resolveMember(ClassTypeProvider.scala:83)
[info]   at io.kaitai.struct.ClassTypeProvider.determineType(ClassTypeProvider.scala:46)
[info]   at io.kaitai.struct.ClassTypeProvider.determineType(ClassTypeProvider.scala:20)
[info]   at io.kaitai.struct.translators.TypeDetector.detectTypeRaw(TypeDetector.scala:61)
[info]   at io.kaitai.struct.translators.TypeDetector.detectType(TypeDetector.scala:25)
[info]   at io.kaitai.struct.precompile.ValueTypesDeriver.$anonfun$deriveValueType$2(ValueTypesDeriver.scala:28)
[info]   at io.kaitai.struct.precompile.ValueTypesDeriver.$anonfun$deriveValueType$2$adapted(ValueTypesDeriver.scala:21)
[info]   at scala.collection.immutable.RedBlackTree$.foreach(RedBlackTree.scala:291)
[info]   ...

Actually, I think, that this is incorrect test. You should check attribute IDs when you defines attribute, not when you use it. Obviously, you use that name with which attribute is defined. I expect, that this test will report unknown attribute BAD even when it is obviously violates ID requirements

[Mingun]

For the same strange reason as in #313, this PR adds new error (in comparison to 83dde4b)

[info] - encoding_str_missing *** FAILED ***
[info]   [encoding_str_missing.ksy: /seq/0:
[info]   	error: string type, but no encoding found
[info]   ]
[info]     did not equal
[info]   [encoding_str_missing.ksy: /seq/0:
[info]   	error: string type, but no encoding found
[info]
[info]   encoding_str_missing.ksy: /seq/1:
[info]   	error: string type, but no encoding found
[info]
[info]   encoding_str_missing.ksy: /instances/baz:
[info]   	error: string type, but no encoding found
[info]   ] (SimpleMatchers.scala:34)

It seems to me, that the test was changed after running tests on master (83dde4b).

@generalmimon, could you review this?