fix: works with unicode password

[vitormattos]

JSignPdf don't works as well at CLI interfaceif the password have unicode chars. As workaround, I changed the password certificate in memory.

When we use a certificate with an unicode char at password will throw this error:

Exception: Error to sign PDF. [
	"FINE Default property file doesn't exists.",
	"FINE Default property file doesn't exists.",
	"INFO Checking input and output PDF paths.",
	"java.io.IOException: keystore password was incorrect",
	"\tat java.base\/sun.security.pkcs12.PKCS12KeyStore.engineLoad(Unknown Source)",
	"\tat java.base\/sun.security.util.KeyStoreDelegator.engineLoad(Unknown Source)",
	"\tat java.base\/java.security.KeyStore.load(Unknown Source)",
	"\tat net.sf.jsignpdf.utils.KeyStoreUtils.loadKeyStore(KeyStoreUtils.java:359)",
	"\tat net.sf.jsignpdf.utils.KeyStoreUtils.getPkInfo(KeyStoreUtils.java:411)",
	"\tat net.sf.jsignpdf.SignerLogic.signFile(SignerLogic.java:154)",
	"\tat net.sf.jsignpdf.Signer.signFiles(Signer.java:246)",
	"\tat net.sf.jsignpdf.Signer.main(Signer.java:139)",
	"Caused by: java.security.UnrecoverableKeyException: failed to decrypt safe contents entry: javax.crypto.BadPaddingException: Given final block not properly padded. Such issues can arise if a bad key is used during decryption.",
	"\t... 8 more",
	"WARNING Keystore was not loaded succesfully. Check if the keystore type, path and password are valid.",
	"SEVERE Problem occured",
	"java.lang.NullPointerException: Keystore was not loaded succesfully. Check if the keystore type, path and password are valid.",
	"\tat net.sf.jsignpdf.utils.KeyStoreUtils.getKeyAliasInternal(KeyStoreUtils.java:224)",
	"\tat net.sf.jsignpdf.utils.KeyStoreUtils.getPkInfo(KeyStoreUtils.java:413)",
	"\tat net.sf.jsignpdf.SignerLogic.signFile(SignerLogic.java:154)",
	"\tat net.sf.jsignpdf.Signer.signFiles(Signer.java:246)",
	"\tat net.sf.jsignpdf.Signer.main(Signer.java:139)",
	"",
	"INFO Finished: Creating of signature failed."
]

[vitormattos]

Wait to review, working to improve performance.

[vitormattos]

The new test use the method sign to call the validation method. To improve the performance of test, I called the validation method directly, to do this, was necessary make this method public.

After performance improvement, test execution time was reduced by half:

[vitormattos]

@jeidison done!
ready for review.

[vitormattos]

Done, I implemented now a mock to exec command and return the methods to be privated