Harden invitee input and contact names

Security audit found two gaps. Sabre only quotes ICS
parameter values containing space, newline, quote, colon,
semicolon, caret, comma or plus, so a bare carriage
return in a contact name would be written into the
serialized event unquoted and break the line structure;
names with control characters are now dropped. The raw
attendee input and the search query had no length
bound, a huge POST field was fully split, iterated and
echoed back on re-render, a cheap CPU sink; both are
now capped, the query at the longest possible email
fragment.

l10n/de.json

@@ -34,7 +34,8 @@
         "Invitees": "Teilnehmer",
         "Email addresses, comma-separated": "E-Mail-Adressen, durch Kommas getrennt",
         "%s is not a valid email address.": "%s ist keine gültige E-Mail-Adresse.",
-        "A meeting can invite at most %d people.": "Ein Meeting kann höchstens %d Personen einladen."
+        "A meeting can invite at most %d people.": "Ein Meeting kann höchstens %d Personen einladen.",
+        "Invitee list is too long.": "Die Teilnehmerliste ist zu lang."
     },
     "pluralForms": "nplurals=2; plural=(n != 1);"
 }

l10n/de_DE.json

@@ -34,7 +34,8 @@
         "Invitees": "Teilnehmer",
         "Email addresses, comma-separated": "E-Mail-Adressen, durch Kommas getrennt",
         "%s is not a valid email address.": "%s ist keine gültige E-Mail-Adresse.",
-        "A meeting can invite at most %d people.": "Ein Meeting kann höchstens %d Personen einladen."
+        "A meeting can invite at most %d people.": "Ein Meeting kann höchstens %d Personen einladen.",
+        "Invitee list is too long.": "Die Teilnehmerliste ist zu lang."
     },
     "pluralForms": "nplurals=2; plural=(n != 1);"
 }

l10n/en.json

@@ -34,7 +34,8 @@
         "Invitees": "Invitees",
         "Email addresses, comma-separated": "Email addresses, comma-separated",
         "%s is not a valid email address.": "%s is not a valid email address.",
-        "A meeting can invite at most %d people.": "A meeting can invite at most %d people."
+        "A meeting can invite at most %d people.": "A meeting can invite at most %d people.",
+        "Invitee list is too long.": "Invitee list is too long."
     },
     "pluralForms": "nplurals=2; plural=(n != 1);"
 }