add check for cast double->float

Script scoring might result in overflow, for example if a user
decides to use the timestamp as a boost. Therefore, check
if cast cuases a huge precision loss. Note that this does
not always prevent casting issues, since SearchScript has two
methods runAsFloat() and runAsDouble(). Depending on the implementation,
the cast check might not help, see for example AbstractFloatSearchScript and
MvelSearchScript.