hicp 0.6.0

• Introduced the global options options("hicp.unbundle"=TRUE), options(hicp.coicop.version="ecoicop-hicp"), options(hicp.all.items.code="00")
• The functions is.coicop(), level(), parent(), child(), aggregate(), and tree() now have the argument settings, which can be used to define a COICOP version (coicop.version), the all-items code (all.items.code), and how bundle codes are treated (unbundle)
• The function is.coicop() now accepts different COICOP versions. The functions level(), parent(), child(), aggregate(), and tree() only process valid COICOP codes and the all-items code.
• Fixed the behavior of aggregate() when the functions jevons(), carli(), and harmonic() are used and no weights w0 are provided
• Fixed a bug in the function chain(), which occurred when the unchained series started in January and by=12. In this case, the index reference period (with value 100) was not correctly detected
• Updated documentation and tests accordingly